At higher speed of Impeller size of granules increases and if high speed is for longer time due to continuous collisions between the particles the size of granules will decrease .
The gap between base of mixing chamber is around 2.0 mm which is enough that the granules pass below the impeller blade without breaking .
Chopper the Science behind
The use of chopper should not be done always as we know the chopper will break the granules.
Firstly look weather active is free flowing or cohesive , weather it lumps or not .Chopper should be used if active is cohesive or forms lumps at the minimum speed after solution addition .
Binder solution addition Science
RMG
Rapid mixer granulator
Binder should be added slowly not suddenly as sudden addition of binder leads to inefficient distribution of binder and may cause hardness variation in tablet .
End point
Ampere load on Impeller and Chopper i.e the current which is used by Impeller and chopper motor to rotate when granules are formed . Ampere load is high in beginning when granulation starts as motors need more power and decreases as end point is reached .
End point could also be determined by ensuring the Vortex formation Generally done by Research and Development personnel during Optimization of batch.
Fill level in RMG
All Mixing chambers have minimum and maximum Fill depth depends upon size of vessel and powder characteristics
Before determining depth of fill points to be considered are
rapid_mixer_granulator
Rapid mixer granulator
How much powder to be granulated is active .
Does the powder Density or Swell on solvent addition and to what extent
Is material constant
Is Dip tube length (Solution entry tube) lesser than the height of powder.
Nature of Granulating solvent / suspension
Surface tension of granulating liquid If surface tension is low larger amount of binder is require to produce same size of granules when compared to higher surface tension binder .
Quantity of liquid binder more the concentration of binder better the granules but batch could become unstable after certain limit .
Viscosity of binder is also an critical operating parameter higher the viscosity of binder larger and denser the granules .
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